Submission #1115108

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115108		_callmelucian	Event Hopping (BOI22_events)	C++14	0 / 100	3 ms	7248 KiB

events

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tpl;

#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())

const int mn = 1e5 + 5;

struct item {
    int L, R;

    item() : L(INT_MAX), R(0) {}
    item (int L, int R) : L(L), R(R) {}

    bool operator < (const item &o) const {
        if (R == o.R) return L < o.L;
        return R < o.R;
    }
} event[mn];

struct IT {
    vector<int> tr;
    IT (int sz) : tr(4 * sz) {}

    int opr (int a, int b) {
        return (event[a].L < event[b].L ? a : b);
    }

    void update (int pos, int val, int k, int l, int r) {
        for (; l < r;) {
            int mid = (l + r) >> 1;
            if (pos <= mid) k <<= 1, r = mid;
            else k <<= 1, k |= 1, l = mid + 1;
        }

        tr[k] = opr(tr[k], val);
        for (k /= 2; k; k /= 2)
            tr[k] = opr(tr[k << 1], tr[k << 1 | 1]);
    }

    int query (int a, int b, int k, int l, int r) {
        if (b < l || r < a) return 0;
        if (a <= l && r <= b) return tr[k];
        int mid = (l + r) >> 1;
        return opr(query(a, b, 2 * k, l, mid), query(a, b, 2 * k + 1, mid + 1, r));
    }
};

vector<int> cmp;
int nxt[18][mn];

int getID (int targ) {
    return lower_bound(all(cmp), targ) - cmp.begin();
}

int main()
{
    freopen("EVENTS.inp", "r", stdin);
    freopen("EVENTS.out", "w", stdout);

    ios::sync_with_stdio(0);
    cin.tie(0);

    int n, q; cin >> n >> q;
    for (int i = 1; i <= n; i++) {
        cin >> event[i].L >> event[i].R;
        cmp.push_back(event[i].L), cmp.push_back(event[i].R);
    }
    sort(all(cmp)), filter(cmp);

    vector<int> ord(n);
    for (int i = 1; i <= n; i++) ord[i - 1] = i;
    sort(all(ord), [&] (int a, int b) { return event[a].R < event[b].R; });

    IT tree(cmp.size());
    for (int i : ord) {
        event[i].L = getID(event[i].L), event[i].R = getID(event[i].R);
        tree.update(event[i].R, i, 1, 0, cmp.size() - 1);
        nxt[0][i] = tree.query(event[i].L, event[i].R, 1, 0, cmp.size() - 1);

//        cout << "next " << i << " -> " << nxt[0][i] << "\n";
    }

    for (int s = 1; s < 18; s++)
        for (int i = 1; i <= n; i++)
            nxt[s][i] = nxt[s - 1][nxt[s - 1][i]];

    for (int i = 0; i < q; i++) {
        int s, e; cin >> s >> e;
        if (s == e) {
            cout << 0 << "\n";
            continue;
        }
        if (event[s].R > event[e].R) {
            cout << "impossible\n";
            continue;
        }
        if (event[e].L <= event[s].R) {
            cout << 1 << "\n";
            continue;
        }

        int ans = 0;
        for (int lift = 17; lift >= 0; lift--) {
            if (event[nxt[lift][e]].L > event[s].R) e = nxt[lift][e], ans |= (1 << lift);
        }
        e = nxt[0][e], ans++;

        if (event[e].L > event[s].R) cout << "impossible\n";
        else cout << ans + 1 << "\n";
    }


    return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen("EVENTS.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
events.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen("EVENTS.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30